Adjustable hydraulic linear decelerator

ABSTRACT

The application discloses an adjustable hydraulic linear decelerator, which may be either of the spring return type having an internal accumulator, or of the air return type having an external accumulator. The device comprises a cylinder having a piston which operates, upon an impact, against hydraulic fluid charged into the cylinder. The cylinder has, along a generatrix, a series of exponentially spaced apertures, and is embraced by a sleeve having along a generatrix, a series of obturating slots of the same minimum axial width as said apertures, and cooperating with said apertures respectively. The sleeve is surrounded by a reservoir tube, annularly spaced therefrom, and is coupled to said tube so that it may be rotated by rotating said tube. The sleeve also has a guide slot cooperating with a pin fixed to said cylinder to limit the extent of rotation of said sleeve to the circumferential extent of said obturating slots. The obturating slots may be angularly disposed with respect to the circumference while the guide slot is circumferential, so that, upon rotation of the sleeve between limits, the slots in effect go from an obturating position to an open position without axial movement of the sleeve. Alternatively, the obturating slots may be circumferential while the guide slot is angularly disposed, so that rotation of the sleeve is accompanied by an axial displacement thereof by substantially the width of the obturating slots. In this case the coupling is by means of a pin and slot connection to provide for the necessary axial movement.

United States Patent [191 Selke et a1.

[ Jan. 1, 1974 ADJUSTABLE HYDRAULIC LINEAR DECELERATOR [75] lnventors: Donald A. Selke; Layne F. Tekulve;

Richard R. Schmid, all of Cincinnati, Ohio [73] Assignee: The Shelter Corporation,

Cincinnati, Ohio [22] Filed: Nov. 8, 1972 [21] Appl. No.: 304,611

[521 U.S. Cl. 267/118, 267/65 R [51] Int. Cl F161 5/00 {58] Field of Search 267/118, 65 R, 65 A, 267/65 B, 65 C, 65 D [56] References Cited UNITED STATES PATENTS 3,339,910 9/1967 Jackson 267/65 R 3,647,199 3/1972 Bhutani et al 267/65 R Primary Examiner-Gerald M. Forlenza Assistant Examiner-Lawrence .1. Oresky A!I0rney.1ohn W. Melville et al.

[57] ABSTRACT The application discloses an adjustable hydraulic linear decelerator, which may be either of the spring return type having an internal accumulator, or of the air return type having an external accumulator. The device comprises a cylinder having a piston which operates, upon an impact, against hydraulic fluid charged into the cylinder. The cylinder has, along a generatrix, a series of exponentially spaced apertures, and is embraced by a sleeve having along a generatrix, a series of obturating slots of the same minimum axial width as said apertures, and cooperating with said apertures respectively. The sleeve is surrounded by a reservoir tube, annularly spaced therefrom, and is coupled to said tube so that it may be rotated by rotating said tube. The sleeve also has a guide slot cooperating with a pin fixed to said cylinder to limit the extent of rotation of said sleeve to the circumferential extent of said obturating slots. The obturating slots may be angularly disposed with respect to the circumference while the guide slot is circumferential, so that, upon rotation of the sleeve between limits, the slots in effect go from an obturating position to an open position without axial movement of the sleeve. Alternatively, the obturating slots may be circumferential while the guide slot is angularly disposed, so that rotation of the sleeve is accompanied by an axial displacement thereof by substantially the width of the obturating slots. In this case the coupling is by means of a pin and slot connection to provide for the necessary axial movement.

6 Claims, 8 Drawing Figures PATENTEDJM new 7 3.782.710

I SHEET 10? 2 ADJUSTABLE HYDRAULIC LINEAR DECELERATOR' BRIEF SUMMARY OF THE INVENTION The present invention provides for adjustability in a relatively inexpensive manner; and the device is simple, and not liable to breakage or malfunction.

The invention is'equally applicable to hydraulic linear-decelerators' of the spring return type, having an inte'rhal accumulator, and to linear decelerators of the air return type, having an external accumulator.

Briefly, the linear decelerator of the present invention comprises a cylinder containing hydraulic fluid, and a piston operating against said fluid when it receives an impact. The outboard end of the piston is of course provided withan impact receiving member. The cylinder'is provided with a number of apertures for the escape of hydraulic fluids; and these are arranged along a" generatrix of the cylinder and are exponentially spaced as is well known in the art. The cylinder is snugly embraced bya sleeve which is provided with a number of obturation'slots, one for each of said apertures; and of the same minimum axial width as said apertiires; The sleeve also has a guide slot cooperating with'a pin fixed to said cylinder, to limit the extent of rotation'of'said-sleeve to the circumferential extent of said obturation slots. The sleeve is surrounded by a reservoir tube, annularly spaced therefrom, and is coupled to said tube so as to be rotated within said limits when said tube is rotated. The obturation slots and guide slots are so arranged that atone limit of rotation the apertures are entirely closed, and'at the other limit of rotationthey are entirely open. Infinite adjustability is provided between said limits. Obturation may be achieved by disposing the obturation slots at an angle to circumference, the guide slots being circumferential. Thus rotation of the sleeve takes place without axial displacement thereof and'theeffective portion of the obturation slots moves gradually across the apertures. The axial displacement between the ends of each obturation slot will be substantially the axial width of an obturation slot. Alternatively, the obturation slots may be circumferential, and the guide slot may be angularly disposed, whereby rotationof the sleeve is accompanied by axial displacement thereof. The amount of displacement between the aforesaid limits will be substantially the axial width of the obturation slots.

The use of external accumulator, air return, arragements for linearde'celeart'or's is well known, and need not be described in detail. Similarly the use of internal accumulator, spring return, arrangements is well known, wherein the internal accumulator comprises a body of nitrogen filled, closed cell, cellular material. One novel feature of the present invention resides in the provision of a shield for said body, to protect it from the jets of hydraulic fluid and turbulence thereof resulting from the linear decelerator receiving an impact load.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS FIG 1 is a longitudinal'cross sectional view of a springreturn, linear hydraulic decelerator having an internal accumulator, according to the present invention; An air accumulator is indicated as an alternative, in broken lines.

FIG. 2 is a cross sectional view taken on the line 2-2 of FIG. 1.

FIGS. 3a, 3b and 3c are fragmentary diagrammatic plan views of the adjusting sleeve, showing the relationship between an aperture in the cylinder and an obturation slot in three positions of rotation of the sleeve, according to one embodiment.

FIGS. 40, 4b and 4c are views similar to FIGS. 3a, 3b and 30, according to another embodiment. I

DETAILED DESCRIPTION Referring first to FIG. 1, there is shown a hydraulic linear decelerator comprising a cylinder 10 within which a piston 11 operates. The piston ll is mounted on the end of a piston rod 12.which, at its outboard end is provided with an impact receivingmember 13.

The cylinder may be formed as a part of a brazement including the head 14 at one end and the head 15 at the other end. Mounting flanges l6 and 17 may be provided for the heads 14 and 15 respectively.

Snugly embracing the cylinder 10 is a sleeve 20. A reservoir tube 21 is annularly spaced from the sleeve 20 and extends between theheads 14'and 15.

It will be noted that the cylinder 10 is provided with a series of apertures 18which are disposed along a generatrix of the cylinder 10 and are arranged in an exponential manner. This sort of arrangement is well known in connection with hydraulic linear decelerators. As the piston 11 moves toward theleft upon receiving an impact, the oil within the cylinder 10 is forced out through the apertures 18 and the piston gradually closes off one aperture after another so as to bring the piston to a gradual stop. Forgetting for a moment the presence of the sleeve 20, the oil which passes through the apertures 18 enters the annular space 22 between the cylinder and the reservoir tube. If the device is a spring return'internal accumulator decelerator, an accumulator member 23 is provided in the space 22 and this member will be described in more detail hereinafter. The piston rod 12 and its associated parts are returned to initial position when the load is removed by means of the spring 24. If the linear decelerator is to be an air return type with an external accumulator, the internal accumulator 23 is omitted as is the spring 24'and instead an accumulator 23a (shown in broken lines) is connected to the flow opening 25 by means of a pipe 26 and air is supplied to the accumulator at a predetermined pressure through the pipe 27.

Returning now to the structure of the cylinder and sleeve and the manner of adjustment of the linear decelerator, the sleeve is provided with a number of slots 30 equal to the number of apertures 18. These slots 30 have an axial extent equal to or greater than the diameter of the apertures 18. Secured to the cylinder is a pin 31' which operates in a slot 32 in the sleeve 20. In this way the pin and slot determine the extent of rotation of the sleeve 20. The extent of this rotation is indicated in FIG. 2 by the angle R.

In the embodiment shown in FIGS. 3a to 30, the slots 30 are disposed at a small angle to the circumference while the slot 32 in which the pin 31 engages is truly circumferential. As seen in FIG. 3a, at one limit of rotation of the sleeve 20, the aperture 18 is completely obturated. At the other end of the limit of movement, as seen in FIG. 3c, the aperture 18 is completely open. In FIG. 3b, at a midpoint, it will be seen that the slot 30 has opened one-half of the aperture 18. Thus, there is provided an infinite adjustability for each of the slotaperture combinations between the fully closed position of FIG. 3a and the fully opened position of FIG. 3c. In this embodiment, the sleeve 20 does not move axially and it is the angularity of the slots which provides the obturation effect. It will be clear that one end of each slot 30 is disposed at an axial distance from the other end of the slot equal to or greater than the diameter of the aperture 18.

According to another embodiment, as seen in FIGS.

4a to 4c inclusive, the slots 30a are truly circumferential but the slot 32 is disposed at an angle as were the slots 30 in FIGS. 3a to 3c. In this embodiment, the sleeve 20 moves axially as it is rotated; and again in FIG. 4a the aperture 18 is completely closed and in FIG. the aperture is completely open, while in FIG. 4b at a midpoint in the rotation of the sleeve 20, the aperture is one-half open. In this embodiment therefore the movement of the slot with respect to the aperture is achieved by an actual axial movement of the sleeve 20 with respect to the cylinder 10.

The sleeve 20 is coupled to the reservoir tube 21 by means of a pin 40. The reservoir tube 21 is preferably provided with a knurled ring 41 which may be rotated manually. By virtue of this construction, as the knurled ring 41 and the tube 21 are rotated, the pin 40 carries with it the sleeve 20. It will be noted that the pin 40 engages in a slot 42 in the sleeve 20. The slot 42 is axial and is only of such width as to allow for the axial movement of the sleeve necessitated in the embodiment described in connection with FIGS. 4a to 4c. There is no play between the pin 40 and the sleeve 20 in a direction normal to the paper. It will be observed that in accordance with conventional practice the inside of the reservoir tube is sealed by means of O-rings at 43 and 44 in conventional manner. As is also well known, means must be provided to permit oil above the cylinder to flow back below the cylinder during a return stroke of the piston rod 12. This is accomplished by means of the usual ring valve 48 operating in an annular recess 45 communicating with the apertures 46 in the end of the piston. The piston rod 12 is sealed by means of the usual glands 47. I

Turning now to the accumulator 23, which is used with a spring return arrangement, as shown in solid lines in FIG. 1, the accumulator comprises a partial sleeve constituted of a nitrogen filled, closed cell, cellular member. The member 23 fills the annular space between the'sleeve and the reservoir tube 21 except for the angular portion indicated at R in FIG. 2 which is the angular extent of the slots 30 and the area through which the pin 31 moves. It should be understood that when an impact is received by the member 13 and the piston 11 is moved toward the left in FIG. 1, the oil is forced from the space within the cylinder through the apertures 18 and slots 30 into the space 22 under great pressure. Thus the jet action and turbulence in the oil tends to destroy the integrity of the accumulator material 23. This problem is overcome, according to the present invention, by the provision of a thin sheet metal shield 50 which extends around the inside of the member 23, and is flanged over the exposed 'ends at 51. This feature adds a great deal to the lifev of the accumulator and preserves it from disintegration.

The diameters of the holes 18 and the dimensions of the slots 30 will naturally depend upon the size of the linear decelerator and the magnitude of the impacts which it must decelerate. It should be pointed out that with very small units the last few of the exponentially arranged holes might have to be so close together that they would interfere. This can be avoided by elongating the holes in a circumferential direction so as to retain the area requirements while also meeting the space requirements.

In filling the linear decelerator with hydraulic fluid, use is made of the fill opening 25. Bleeding openings are provided which, when the unit has been fully charged, is plugged by means of the plug 60. At 61 is shown a set screw by means of which the position of the sleeve with respect to the cylinder may be fixed after a desired position of adjustmenthas been found. It will be understood that with a spring return device the filler opening 25 will be plugged in a conventional manner and if the device is to be an air return device, then the tube 26 is attached in place of the filler plug.

It will be understood that numerous modifications may be made without departing from the spirit of the invention. No limitation not expressly set forth in the claims is intended and no such limitations should be implied.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A linear decelerator comprising a cylinder, and a piston reciprocable therein, said cylinder containing hydraulic fluid ahead of said piston, a rotatable sleeve surrounding said cylinder, a number of apertures in said cylinder, exponentially spaced along a generatrix of said cylinder, a number of obturation slots in said sleeve equal to the number of said apertures and exponentially spaced along a generatrix of said sleeve, the axial extent of each of said apertures being substantially equal and the axial extent of said obturation slots being at least as great as that of the respective apertures, there being an obturation slot for each aperture, a reservoir tube surrounding said sleeves in annularly spaced relation thereto, means coupling said sleeve to said reservoir tube so as to be rotatable by rotation of said reservoir tube, a guide slot in said sleeve and a pin secured to said cylinder and engaging in said guide slot to limit the rotational movement of said sleeve to the circumferential length of said obturation slots, rotational movement of said sleeve producing an axial displacement of the obturation slots with respect to their respective apertures; said obturation slots at one limit of rotation of said sleeve obturating said apertures, and at the other limit of rotation of said sleeve fully opening said apertures, whereby the action of said decelerator may be adjusted by rotation of said reservoir tube.

2. The structure of claim 1, wherein said obturation slots are disposed parallel to each other and at an angle to the circumference of said sleeve, and said guide slot is circumferentially disposed, whereby rotation of said sleeve is circumferential without axial displacement, and obturation is obtained by virtue of the angular disposition of said obturation slots.

3. The structure of claim 1, wherein said obturation slots are disposed circumferentially, and said guide slot is disposed at an angle to the circumference of said closed cell, cellular member is disposed within said reservoir tube and surrounding said sleeve except over the circumferential extent of said obturation slots, to serve as an internal accumulator.

6. The structure of claim 5, wherein a thin sheet metal shield is provided to protect said internal accumulator from hydraulic fluid jets and turbulence, said shield being of substantially the axial length of said accumulator, being disposed between said accumulator and said sleeve, and having flange portions extending around the circumferential ends of said accumulator.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 0 0710 Dated January 1, 1974 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 50, "flow" should be fill "25" with a lead line tothe rectangular configuration into which the pipe 26 leads.

Signed and sealed this 9th day of April 1975.

( 3 BAR At t e s t I RUTH C. EL ISON Commissioner of Patents Attesting Officer and Trademarks Inventor s Donald A. Selke, Layne F. 'Iekulve, Richard S. Schmid I In the Drawing, Figure 1, there should be a reference numeral FORM po'wso USCOMM-DC some-"P es U.S. GOVERNMENT PR'NTING OFFICE l 9.9 0-;66-334 z 

1. A linear decelerator comprising a cylinder, and a piston reciprocable therein, said cylinder containing hydraulic fluid ahead of said piston, a rotatable sleeve surrounding said cylinder, a number of apertures in said cylinder, exponentially spaced along a generatrix of said cylinder, a number of obturation slots in said sleeve equal to the number of said apertures and exponentially spaced along a generatrix of said sleeve, the axial extent of each of said apertures being substantially equal and the axial extent of said obturation slots being at least as great as that of the respective apertures, there being an obturation slot for each aperture, a reservoir tube surrounding said sleeves in annularly spaced relation thereto, means coupling said sleeve to said reservoir tube so as to be rotatable by rotation of said reservoir tube, a guide slot in said sleeve and a pin secured to said cylinder and engaging in said guide slot to limit the rotational movement of said sleeve to the circumferential length of said obturation slots, rotational movement of said sleeve producing an axial displacement of the obturation slots with respect to their respective apertures; said obturation slots at one limit of rotation of said sleeve obturating said apertures, and at the other limit of rotation of said sleeve fully opening said apertures, whereby the action of said decelerator may be adjusted by rotation of said reservoir tube.
 2. The structure of claim 1, wherein said obturation slots are disposed parallel to each other and at an angle to the circumference of said sleeve, and said guide slot is circumferentially disposed, whereby rotation of said sleeve is circumferential without axial displacement, and obturation is obtained by virtue of the angular disposition of said obturation slots.
 3. The structure of claim 1, wherein said obturation slots are disposed circumferentially, and said guide slot is disposed at aN angle to the circumference of said sleeve, whereby rotation of said sleeve is accompanied by axial displacement thereof to produce obturation of said apertures.
 4. The structure of claim 3, wherein the coupling between said sleeve and reservoir tube comprises a pin fixed with respect to said reservoir tube, said pin cooperating with an axial slot in said sleeve, said axial slot having a width to snugly accommodate said pin, and a length sufficient for axial movement of said sleeve between obturating and fully open positions of said obturation slots.
 5. The structure of claim 1, wherein a nitrogen filled, closed cell, cellular member is disposed within said reservoir tube and surrounding said sleeve except over the circumferential extent of said obturation slots, to serve as an internal accumulator.
 6. The structure of claim 5, wherein a thin sheet metal shield is provided to protect said internal accumulator from hydraulic fluid jets and turbulence, said shield being of substantially the axial length of said accumulator, being disposed between said accumulator and said sleeve, and having flange portions extending around the circumferential ends of said accumulator. 